That is a state we did not expect. We will solve this issue in some weeks.
there are 2 ways you could solve this problem:

Add a "Top Frame"
Go to screen options (top right) and enable the Gridder JSON box. -> go to Gridder JSON Box and replace
"rowGutters": [],
with
"rowGutters": [ {} ],
-> now save the post and you should see an empty row.